The third chapter in the ongoing saga of the "first direct image of gravitational waves through the primordial sky" has been written. The first chapter was in March of last year when the BICEP2 team announced that it had observed the portion of cosmic background radiation (the "fossil radiation" from the Big Bang) generated by gravitational waves. This would have been the first observation of the cosmological effects of the elusive phenomenon predicted by Einstein's theory of General Relativity. 

Such a discovery would be a milestone in the history of astrophysics, cosmology and physics of fundamental forces. For that reason, the most obvious question - 'Are we sure that the signal is not the effect of contaminants due to the polarized emission of our Galaxy?' was ignored even though the paper stated that current knowledge indicates that contaminating radiation is small compared to the observed signal. 

In Chapter Two, the Planck team said their data showed that polarized galactic radiation is not negligible in these measurements. They weren't just being conservative, their instrument observes the same portion of sky as BICEP2, but with a far wider range of frequencies. 

Now in Chapter Three, on-ground analysis by BICEP2 and Planck scientists confirm the Planck view: though data from a new instrument (Keck) was also examined by BICEP2, they confirm that the galactic contaminants are sufficiently intense to preclude any definite statement concerning the presence or absence of cosmological gravitational waves.

That is science speak for 'it is not what they thought'.

Deflecting light from the Big Bang. Credit: ESA

"Our work isn't over", concludes  Carlo Baccigalupi, SISSA cosmologist and one of the authors of the paper. "Current experiments (including BICEP2) and future projects (a new satellite, a 'descendent' of Planck called CORE+ has just been proposed to the European Space Agency) have understood the message of Planck and BICEP2 very well, and are planning to equip themselves with technology capable of observing the Galaxy with very sharp eyes, to be able to distinguish it from the signal of the Big Bang, if indeed it did emit gravitational waves".